Conventionally, various kinds of head-up display devices have been proposed. Such a head-up display device displays a virtual image by projecting a display light, which is emitted from a liquid crystal display provided with an illumination optical system including a light source and a liquid crystal display panel, on a viewpoint range (hereinafter, referred to also as an eye box) of an observer (mainly a driver in the case of a head-up display device for a vehicle), via a projecting member constituted by a windshield and a dedicated combiner of a vehicle. PTL 1 discloses an example of a conventional head-up display device. The head-up display device is provided with a condenser lens for converging an illumination light emitted from a light emitting element, a lenticular lens for spreading the illumination light converged by the condenser lens in at least lateral direction, and a converging lens having a toroidal surface, as an illumination optical system.
According to a head-up display device using the illumination optical system as described above, it is possible to transparently illuminate a display member so as to deal with an eye box of an observer. Therefore, it is possible to display a virtual image with high brightness.